The present invention relates to a process for producing a lancing element for withdrawing bodily fluid in which a flat-shaped member is formed from a flat material by applying a mask and allowing an etching agent to act upon it. At least a part of the flat-shaped member is shaped as a tip for piercing into a body part of a test subject.
Lancing elements of this type are used for the analysis of very small amounts of fluid, especially in bioanalytics, such as those which are withdrawn in situ as capillary blood for blood glucose determinations. Such microfluidic systems, in addition to the microscopic volumes (microliters and less), are also characterized by structural elements of increasingly smaller dimensions which use capillary forces and can be implemented in so-called disposables in a suitable manner for mass production. Although manufacturing processes, especially in the form of mask etching (photochemical etching), are known from the field of semiconductor technology for highly-integrated systems, the materials used cannot generally be used for mechanically stressed structures due to their brittleness. When biocompatible materials such as steel are etched, a problem arises with conventionally shaped-complementary etch masking in which the generated lancing structures are rounded off at the tip and thus do not provide a particularly optimal puncture.
An etching process for producing surgical needles is known from U.S. Pat. No. 4,777,096, in which the etch mask extends beyond the tip to be formed in a distally blunted shaping area and is constructed to prevent rounding of the tip. However, this mask overhang is shorter than the undercutting width of the etching agent so that the tip is shaped by a combined lateral and frontal etching action which only slightly reduces the problem of blunting.